Oven door window



April 6, 1965 R. A. KINKLE 3,177,334

OVEN DOOR WINDOW Filed March ll, 1963 INVENTOR. ROBERT A. K1 NKLE BY a-Mfw HIS ATT'ORNEY 3,177,334 OVEN DOR WHNDW Robert A. Kinlde, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed Mar. 11, 1963, Ser. No. 264,374

3 Claims. (Cl. 219-1055) The present invention relates to a viewing window in an oven door and particularly for a door of an electronic oven that is supplied with both microwave and radiant energy for cooking purposes.

It is not possible to use the conventional double glass pane Window unit for the door of an electronic oven because it is necessary to prevent the escape of the micro- Wave radiation from the oven cavity into the room. Various designs in the past have used a metallic coating on a glass panel or a metal screen in combination with the glass, and both of them were properly grounded to the door to prevent microwave leakage. This grounding function usually is accomplished by using a compressible metal braid gasket between the metal film or screen Wire and the inner door liner. There are several major disadvantages with designs of the described type. The first is that the gasket must ground the metal film or Wire screen properly throughout the life of the door or else the Window will allow excessive microwave leakage. The second and perhaps major disadvantage of the prior art designs is that if the glass panel containing the metal should crack or shatter for any reason, it would allow excessive micro- Wave leakage. In any event, a design of this type does not lend itself to field replacement by the average range serviceman because of the rather critical microwave grounding procedure.

The principal object of the present invention is to design a window for an oven door that is usable with an electronic oven supplied with microwave energy where the leakage of microwave energy through the window is prevented by a perforated plate that is an integral part of the door structure.

A further object of the present invention is to provide a combined electronic and electric oven with an oven door having a window with both a microwave radiation barrier as well as sealed glass panes for preventing the escape of radiant energy, smoke, odor and vapors; where the microwave barrier cannot be tampered with for this might possibly destroy its integrity.

The present invention, in accordance with one form thereof, relates to a door for use with an oven cavity that is adapted to be supplied with both microwave and radiant energy. The oven door is provided with a window opening for viewing within the cavity. This window presents the problem of preventing the leakage of microwave energy. Also, it is desirable to provide a glass Window unit that serves as a thermal and vapor barrier. Accordingly, the oven door is provided with a perforated radiation barrier that precludes the escape of microwave energy through the window opening without substantial interference with viewing. This barrier is made integral with the door so that the integrity of the radiation barrier cannot be tampered with. Means are also provided for sealing a glass pane over the microwave barrier and sealing a second glass pane to a spacer member to provide a dead air space between said panes.

My invention will be better understood from the following description taken in conjunction with the accompanying drawing and its scope will be pointed out in the appended claims.

FIGURE l is a perspective view of a free-standing range having an oven with a door containing the window structure of the present invention;

FIGURE 2 is a cross-sectional elevational view of a United States Patent O 3,177,334 Patented Apr. 6, 1965 lCe door taken on the line 2-2 of FIGURE 1 and shown with the door arranged in a Vertical position to illustrate the relationship between the door structure, the microwave barrier and the double panes of glass; and

FIGURE 3 is a fragmentary view of one corner of the microwave barrier separated from the oven door and showing a pattern of small openings in the barrier to preclude the escape of microwave energy without substantial interference with viewing.

Turning to a consideration of the drawing and in particular to FIGURE l, there is shown a free-standing electric range comprising a cabinet structure or range body 19 that includes a top cooking surface 11 and an oven cavity 12 located beneath the cooking surface as in most standard ranges, and a control panel 13 located in a bacl'- splasher at the back of the range and above the cooking surface 11. A plurality of surface heating units 14 are provided on the cooking surface 11, it being understood that each heating unit has a separate selector switch 15 located in the backsplasher and cooperating with the heating unit to govern the various heating levels of the unit.

It should be appreciated that the oven cavity 12 is forrned by a Cooperation between a box-like oven liner 16 and a front-opening drop door 17 for gaining access to the oven cavity. Heating means must be provided for the oven to perform the various cooking Operations. This particular oven is first designed to perform conventional cooking Operations by using a pair of metal-sheathed resistance heating elements; there being a lower bake unit 18 arranged adjacent the bottom wall of the oven liner and an upper broil unit 19 which is only slightly visible adjacent the top wall of the oven liner. In addition to the conventional radiant heating energy, this oven is designed to cook foods with microwave energy as is generally taught in the co-pending application of Louis H. Fitzrnayer, Serial No. 135,582, entitled Combination Electric and Electronic Ovens, which was filed in the Patent Office on September 1, 1961, and is assigned to the General Electric Company, the assignee of the present invention.

Actually, very little of the electronic gear is illustrated in the drawing except for a radio interference door gasket 23 fastened on the front of the range body 10 for sealing the gap between the 'oven door and the range body when the door is in its upright closed position. A second element which is peculiar to this type of electronic oven is a perforated turn-table 24 arranged just above the bake unit 18 and having a generally central pivotal axis. This turn-table is provided to support containers of food that are to be cooked either by the microwave energy or by both the radiant energy of the resistance elements 18 and 19 and the microwave energy. As is well understood in this art, the microwave energy is present in the oven cavity in the form of a standing wave of non-uniform field intensity. Accordingly, in order to obtain even cooking of the food, the food is placed on a turn-table that is capable of moving slowly through the mode pattern so as to expose the food to various portions of the wave energy.

It is also desirable to combine the radiant energy with the microwave energy for cooking certain foods such as cakes and roasts where it is important to brown the food from the outside. The turntable 24 is preferably made of thin metal such as aluminum or cold rolled steel in order to obtain the lowest cost, although it should be understood that Ceramic or high temperature glass material could be substituted therefor. The turn table is provided with a plurality of openings 25 (only a few of which are shown) so that the food may be exposed to the radiant energy and circulating hot air coming ofi of the lower bake unit 18 positioned beneath the table.

Perhaps it would be well, in order to obtain a proper aivrsaa background for this invention, to mention briefiy the general arrangement of the electronic -gear'that is designed for this oven as is fully disclosed in the above-mentioned Fitzmayer application Serial No. 135,582. In a Conventional free-standing range, the space below the oven cavity 12 serves as a storage drawer as at 27 (for pots and pans and similar utensils, but this storage space is eliminated in the present range. This space is occupied by a microwave generator in the form of a magnetron tube which serves as a source of ultrahigh frequency eleetromagnetic wave energy for the oven cavity 12. The operating frequency for this magnetron tube happens to be in the order of magnitude of 915 mc. The tube is provided with a power supply which is operable from a low frequency, low voltage A.C. supply source to provide and control a D.C. output voltage and consequently the RF. power output of the mag-netron tube. The microwave energy from the magnetron is transmitted to the oven cavity 12 by way of a transmission line which extends :from beneath the oven cavity up the back wall and across the portion of the top wall of the oven liner and is joined toa feed box positioned thereon. A suitable tuning device for the magnetron and the transmission line is provided in the feed box for tuning the system and obtaining more eflicient utilization of the wave energy. Lastly, the wave energy enter's the oven cavity through the top wall of the oven liner.

Attention will now be `directed to the structure of the door 17 and specifically to a design of a window 29 carried by the door. The door 17 includes an outer decorative panel 3d with folded back peripheral flanges 31 into which is positioned an inner door liner 32. Sandwiched between the outer 'panel 3th and the inner door liner 32 is suitable thermal insulating material 33 such as fiberglass as is best seen in FIGURE 2. The lower edge of the inner door liner 32 is in'terlocked with the lower edge of the outer panel 3h and the door is held together by a pair of fastening screws M seen on the inside of the door and which extend through the door and fasten into a door handle 35. Suitable hinges as at 36 are provided at each side of the range adjacent the lower edge of the door so that the door may pivot between a substantially horizontal open position to a substantially closed Vertical position. Hinge levers 37 are also fastened to the door and they each have an innermost end that extends into the range body for cooperation with spring means (not shown) that serve as a door counterbalancing system as is well understood in this art.

Looking now at FIGURE 2, the main elements shown are the outer panel 30, the inner door liner 32 and the thermal insulation 33 sandwiched therebetween. A generally rectangular window u`nit 29 is provided in the central :portion of the door. There is a rectangular opening 40 in the outer panel 30, which opening is defined by the continuous inner flange 41. The inner door liner 32 is provided with a perforated window opening in the form of the perforated panel 42 that is either an integral part of the door liner and merely provided with a plurality of small openings or perforations 43, or it is a fiat perforated plate 42 as is shown in FIGURE 3 which is welded around its periphery to a generally rectangular opening formed in the inner door liner 32. In any event, this perforated panel 42 is an integral part of the door liner and its openings encompass an area that is generally comparable to the window opening 40 in the outer panel. This perforated panel 42 serves as a microwave radiation barrier to preclude the escape of such energy from the cavity through the window without substantial interference with viewing t within the oven cavity.

In a combined electric and electronic oven such as is disclosed above, it is necessary to prevent both microwave radiation leakage and radiant heat energy loss through the window. The perforated metallic panel 42 prevents microwave radiat-ion leakage and a pair' of glass panels 46 and 47, `when properly arranged, would greatly ,reduce the radiant heat 105.5 through the window. The

glass panels 4d and 47 serve the single purpose of preventing an excessive amount of conventional heat leakage as in a standard oven door window application. In summary, the microwave terminating surface is completely i'ndependent of the glass panels so that gasket leakage and glass breakage no longer :present a microwave radiation hazard as in prior art designs. In the event that one or more of the glass panels become cracked or broken, they may be replaced by the average range serviceman without fear of an improperly grounded microwave Shield.

Going back to FIGUR'E 2, the innermost glass panel 4-6 is adapted to be sealed over the radiational barrier 42 by use of a resilient gasket member 48 that encompasses the periphery of the pane 46. and is sandwiched between said pane and the inner door liner by a plurality of L-bolts 49 which are provided with fastening nuts 59 within the door structure. The opposi'te end of each L-bolt cooperates with a frame-like trim strip 51 which hides the gasket 48 and presents a neat appearance for the window opening. The second glass pane 47 is 'spaced from the first pane 46 by a spacer member 52 which is a continuous frame member so that the pane 47 may be held over the face of the, spacer by an encompassing split channel member or strap 54 where the split end is .fastened together by tabs (not shown) or the like. A simple resilient gasket 53 is interposed beneath the channel member to thereby prevent looseness of the pane 47 with respect to the spacer. Lastly, an outer frame member 58 is positioned against the outer face' of the pane 47 and is held in place by the channel member 54. A continuous gaske-t 55 is provided between the perforated panel 42 and the adjacent portion of the spacer 52 in order to di'scourage or prevent moisture and vapors :front entering between the two glass panes 4.6 and 47, as well as to discourage or prevent movement of air between the two panes so as to provide Va substantially dead air space and provide a better insulating structure to reduce 'radiant energy leakage. The first pane 46 is fastened to the inner door liner by means of the L-bolts 49 as mentioned previously, while the second glass pane 47 and its supporting spacer 52 a-nd trirn frame 58 are also supported as a unit 'from the inner door liner 32. by means of a plurality of spaced clip members 56 which engage the channel members 54 at one end and are fastened to the inner door liner 32 at the other end by means of the fastening screws 57. This construction makes for ease in assembling the window unit in the door in that the window bccomes an integral part of the inner door liner, and it is a simple matter to fa'sten the inner door liner to the outer panel 3h as will be well understood by those skilled in this art. V

Modifications of this invention will occur to those skilled in this art, therefore, it is to be understood, that this invention is not limited to the particular embodiments disclosed, but that it is in'tended to cover all modifications which are within the true spirit and scope of this invention as claimed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electronic oven comprising metallic walls defining an oven cavity adapted to be supplied with both micro- Wave and radiant energy, one of said walls having an opening therein, a metal door adapted to close the opening, said door comprising an outer panel and an inner door liner, the outer door panel having a window opening 'for accommodating viewing within the oven cavity, the inner door liner having a perforated portion overlying the window opening and having a series of small openings closely spaced .from each other to preclude the escape of mirowave energy from said cavity through said window opening without substantial interference with viewing, a glass pane sealed over the outermost surface of the per- 'forated por'tion of the inner liner of the door, a continuous frame-like spacer member on the opposite side of the inner liner' arranged around the periphery of the perforated portons, and a second :pane of glass sealed across the face of the spacer member.

2. An outer door adapted for use with walls that define a cavity that is supplied with both microwave a'nd radiant energy, said door comprising an outer panel and an inner door liner, the outer door panel having a window opening for accommodating viewing within the oven cavity, the inner door liner having a perforated panel formed integrally therewith and overlying the window opening to provide reduced visibility for viewing Within the cavity while precluding the escape of microwave energy from said cavity through said window, a first pane of high temperature glass covering the perforated panel, and sealing means arranged around the periphery of the glass to limit the escape of radiant heat energy, and a second high temperature glass pane arranged on the opposite side of the perforated panel but spaced therefrom by a continuous spacer member arranged around the periphery of the perforated panel, and sealing means for sealing the second glass to the spacer member, and another sealing means for sealing the spacer member to the perforated panel so as to form a dead air space between the two panes of glass, and fastening means for supporting the second glass and the spacer member to the inner door liner.

3. In a door adapted for use with an electronic oven that is supplied With both microwave and radiant energy, the door having an outer panel and an inner door -linner that are both provided with aligned window openings therein, the window opening in the inner door liner being represented by a perforated panel having a plurality of small openings closely spaced from each other to preclude the escape of microwave energy from said cavity through said window opening Without substantial interference with viewing, a first pane of glass assembled over the perforated window opening in the inner door liner, and gasket means sealing the periphery of the first glass pane to the inner door liner, a frame-like spacer member sandwiched between the window opening in the outer panel and the window opening in the inner door liner, gasket means for sealing the spacer member to the inner door liner, a second glass pane assembled over the spacer member adjacent the window opening in the front panel, and fastening means -for joi'ning the spacer member and second glass pane to the inner door liner.

References Cited by the Examiner UNITED STATES PATENTS 2,710,994 6/55 Mills 126-200 2,888,543 5/59 Haagensen 219-1055 2,958,754 11/60 Hahn 219-1055 3,088,453 5/ 63 Grah-n et al 126-200 RICHARD M. WOOD, Primary Examiner. 

1. AN ELECTRONIC OVEN COMPRISING METALLIC WALLS DEFINING AN OVEN CAVITY ADAPTED TO BE SUPPLIED WITH BOTH MICROWAVE AND RADIANT ENERGY, ONE OF SAID WALLS HAVING AN OPENING THEREIN, A METAL DOOR ADAPTED TO CLOSE THE OPENING, SAID DOOR COMPRISING AN OUTER PANEL AND AN INNER DOOR LINER, THE OUTER DOOR PANEL HAVING A WINDOW OPENING FOR ACCOMMODATING VIEWING WITHIN THE OVEN CAVITY, THE INNER DOOR LINER HAVING A PERFORATED PORTION OVERLYING THE WINDOW OPENING AND HAVING A SERIES OF SMALL OPENINGS CLOSELY SPACED FROM EACH OTHER TO PRECLUDE THE ESCAPE OF MICROWAVE ENERGY FROM SAID CAVITY THROUGH SAID WINDOW OPENING WITHOUT SUBSTANTIAL INTERFERENCE WITH VIEWING, A GLASS PANE SEALED OVER THE OUTERMOST SURFACE OF THE PERFORATED PORTION OF THE INNER LINER OF THE DOOR, A CONTINUOUS FRAME-LIKE SPACER MEMBER ON THE OPPOSITE SIDE OF THE INNER LINER ARRANGED AROUND THE PERIPHERY OF THE PERFORATED PORTIONS, AND SECOND PANE OF GLASS SELED ACROSS THE FACE OF THE SPACER MEMBER. 